Contract Law: Defenses against formation - Duress/Coercion and Undue influence

In jurisprudence, duress or coercion refers to a situation whereby a person performs an act as a result of violence, threat, or other pressure against the person. Black's Law Dictionary (6th ed.) defines duress as "any unlawful threat or coercion used... to induce another to act  in a manner  otherwise would not ". Duress is pressure exerted upon a person to coerce that person to perform an act they ordinarily would not perform. The notion of duress must be distinguished both from undue influence in civil law. In criminal law, duress and necessity are different defenses.

Duress has two aspects. One is that it negates the person's consent to an act, such as sexual activity or the entering into a contract; or, secondly, as a possible legal defense or justification to an otherwise unlawful act. A defendant utilizing the duress defense admits to breaking the law, but claims that he/she is not liable because, even though the act broke the law, it was only performed because of extreme unlawful pressure. In criminal law, a duress defense is similar to a plea of guilty, admitting partial culpability, so that if the defense is not accepted then the criminal act is admitted.

Duress or coercion can also be raised in an allegation of rape or other sexual assault to negate a defense of consent on the part of the person making the allegation.

In jurisprudence, undue influence is an equitable doctrine that involves one person taking advantage of a position of power over another person. This inequity in power between the parties can vitiate one party's consent as they are unable to freely exercise their independent will.

In contract law.

Where it is established that a plaintiff was induced to enter into a contract or transaction by the undue influence of the defendant, the contract may be rendered voidable. If undue influence is proved in a contract, the innocent party is entitled to set aside the contract against the defendant, and the remedy is rescission.

As the law of undue influence was applied and developed by the Court of Chancery, it developed into two distinct classes: ‘actual’ undue influence and ‘presumed’ undue influence.